The present inventio relates to the air-fuel ratio controlling operation of an engine having an automatic change gear of electronic control type.
Generally, the electronic control type automatic change gear, which is well known and is actually in general purpose use, may select when necessary a power mode where the speed change gear may be automatically controlled in accordance with a first shift pattern predetermined with emphasis on the engine output and an economy mode where the speed change gear may be automatically controlled.
As the improvement in the engine output performance and the improvement in the fuel cost performance are basically contradictory demands in terms of the fuel control, the two modes try to positively attach importance to one of these two demands and provide a correlation of the demand with respect to control of the fuel (air-fuel ratio).
In the arrangement disclosed in, for example, Japanese Patent Application Laid-Open publication Tokkaisho No. 59-134338, a fuel controlling system is proposed wherein the high load increment factor is adapted to be set larger when the power mode is selected than when the economy mode is selected. Also, for example, in Japanese Patent Application Laid-Open publication Tokkaisho No. 60-104742, a fuel controlling system is proposed wherein the high load increment region for the high load increment is adapted to be enlarged more when the power mode is selected than when the economy is selected.
Such a fuel controlling system is related to the adoption of a shift pattern wherein the power mode is adapted to be shifted up on the side of the higher speed, and the higher load at the high load operation of the engine. On the other hand, in the low speed and low load operation of the engine, the special difference does not exist between both the modes; that is, there is no special difference regardless of whether the power mode is selected or the economy mode is selected, and special consideration is not given to the fuel control.
Accordingly, if the power mode is selected through the expectation of the strong acceleration in, for example, the start of an automobile, the substantial difference does not exist between the two modes in the low speed and low load region, so that the expected acceleration feeling, and output feeling are not provided in the start.
Namely, as disclosed in the specifications of the domestic applications in Japanese Patent Application Laid-open publication Tokkaisho No. 59-134338, and Japanese Patent Application Laid-open publication Tokkaisho No. 60-104742, the conventional system is directed to the high load enrich. In the conventional system, even if the power-shift pattern is selected, the air-fuel ratio and output of the low load region remains unchanged with respect to the economy-shift pattern, so that the start acceleration performance with the power-shift pattern has no superiority over the economy-shift pattern.
Also, Japanese Patent Application Laid-open publication Tokkaisho No. 59-128976, and Japanese Patent Application Laid-open publication Tokkaisho No. 59-128977 are adapted to make the ignition time later, based on the consideration that knocking is likely to be caused when the power shift pattern is selected relative to when the economy shift pattern is selected, and have nothing to do with the art idea of this case. To delay the ignition time is to lower the engine output, and in the prior art, it is said that the start acceleration in the power-shift pattern is deteriorated.